Method of injection moulding

ABSTRACT

A resin moulding is produced by introducing molten synthetic thermoplastic resin (19) into a mould cavity (13), sufficient to fill completely the mould cavity. Subsequently, during the cooling of the resin, pressurised gas is introduced into the resin within the mould cavity. The resin moulding cools and hardens in the mould cavity whilst the gas is maintained under pressure. The mould cavity is designed to manufacture mouldings with unevenly distributed thick walled sections (3) connected to at least one gate (4;44) for the introduction of the pressurised gas, which flows only within the resin forming the thick walled sections and immediately adjacent areas of the moulding thereby taking up the shrinkage in the resin.



